A fluid energy machine such as this is already known from PCT/EP2007/051393. One particular field of application for machines such as these is the compression of natural gas which is no longer fed by means of a platform for maritime resources but is compressed directly on the sea bed under the sea and is preferably passed by means of an appropriate pipeline to a land station. This application is particularly financially attractive, because conventional platforms can be omitted and, in a corresponding manner, their immense operating costs as well.
Complex development projects are currently searching for a solution for a compression unit which is matched to the severe conditions involved in compression under the sea. In addition to the difficulty of the chemically aggressive process fluid, which has not been purified and is subject to a continuously decreasing, fluctuating pressure, whereby this process fluid has to be compressed, this process fluid is in some cases liquid and in some cases gaseous, and access to the compressor unit is, of course, extremely difficult, as a result of which the unit preferably has to be designed to require no servicing or to be 100 percent available. In addition, the process medium is chemically aggressive, in the same way as the surrounding medium, and, for environmental protection reasons, there must be no exchange between the process medium and the surrounding medium, or between other working fluids and the surrounding medium.
One particular requirement is represented by the bearing for a rotor of a fluid energy machine such as this, which should preferably not require a working fluid, since any preparation or exchange with a land station would be too complex.
In addition, the rotor bearing must also comply with very stringent requirements for availability, fail safety and emergency running characteristics. With the rotor having a weight of several tons and a rotation speed of up to 20 000 revolutions per minute, a bearing such as this is subject to considerable requirements, as a result of which magnetic bearings are preferred at this point, both for the radial bearing and for the axial bearing. A further advantage of magnetic bearings is that they can be encapsulated, thus allowing the process fluid to flow around the units, as well. In addition, magnetic bearings do not require any working fluid, which could contaminate the surrounding medium or the process fluid.